Pulpwood grinding apparatus



1963 HORNBOSTEL 3,

PULPWQOD GRINDING APPARATUS Filed Dec. 51. 1959 Z/ya/ f/arn basis!United States Patent M 3,077,310 PULPWOOD GRINDHNG APPARATUS LloydHornbostel, Eeloit, Wia, assignor to ltleloit iron llorirs, Beloit, Wis,a corporation of Wisconsin Filed Dec. 31, 1959, iscr. No. 863,295 2Claims. (Cl. 241-280) The present invention relates broadly to the artof pulp production, and is more particularly concerned with novel methodand apparatus for grinding pulpwood featuringmovement of a pulp stoneand pocket relative to one another, whereby there is obtained'pulp ofconsistently uniform quality at substantial power economies.

Since the advent of the early pulpwood grinders using j-ackscrews and acar jack for maintaining pressure and down to the modern high productionmagazine grinders and continuous grinders of the ring or chain feedtypes, it has been found difficu'lt to produce consistently uniformpulp. One explanation for this is the great number of variables in thepulping process, and among those of considerable importance are thesharpness of the pulp stone, the moisture content of the pulp wood andthe pulpwood density.

To explain, an accepted control used in the manufacture of pulp isfreeness or measurement of the drainage characteristics. Since all pulpis at one time in a suspended form, in order to make a sheet of paperthe water must be removed, and'theease or lack of ease with which thismixture, or slurry, will drain is referred to as free ness or slowness.A free stock is usually composed of relatively long, coarse fibers, oris a stock from which the fines or flours (gelatinous bits of fracturedfibers) have been removed; while a :slow stock generally consists ofshort, fine, well-fibrillated fibers intermixed with fines. Now, in pulpgrinding, freeness changes markedly from the time of sharpening the pulpstone until sharpening is again required. The sharp stone tends to cutthe fibers and decreasethefines, whereas asthe stone becomes worn, theextent of cutting decreases and the rubbing and refining action has theefiect of producing more fines and greater fibrillation;

The variable of pulpwood moisture content bears importantly on theefiiciency of the pulping operation, since when the wood is relativelywet the fibers separate more easily, their strength'is greater and thepower consumption is lower. While eitorts are made by soaking or likeprocedures to have at least 30% moisture content, it is apparent thatthis condition cannot always be attained and a uniform moisture contentfor a particular load of pulpwood cannot be efliciently accomplished,even when pre-soaking is used.

Accordingly, to compensate for moisture content and density variations,while striving for consistently uniform pulp quality, the grindingpressure or unit loading is adjusted or varied. The pulpwood pocket,however, of the prior art presents a relatively large contact area botharcuately and axially, and the power requirements to vary the loadingare therefore substantial. As is known, the efiiciency of the pulpingprocess is expressed in terms of horsepower per daily ton of fiber, andit can therefore be seen that when wide variations in grinding pressureor load required to obtain optimum unit loading for consistent pulpquality are necessary, the pulping efficiency is substantiallydiminished.

It is accordingly an important aim of the present invention to providemethod and apparatus for pulpwood grinding productive of uniformlyconsistent pulp quality at minimum power requirements.

Another object of this invention lies in the provision of improvedstructures and procedures for producing pulp, wherein the pulp stone andpocket are moved relative to one another to vary the contact area ofsaid stone artists Patented Feb. 12, i953 in abrasive engagement withpulpwood supported by said pocket, producing as among the advantagesreduced stone wear.

Another object of the instant invention is to provide apparatus forgrinding pulpwood to obtain pulp there from, comprising a rotatablegrinding member, a housing for pulpwood positioned adjacent saidgrinding member, force applying means for advancing said pulpwood intogrinding contact with said grinding member, and means for effectingrelative movement between said grinding member and housing to vary thecontact area of said member in abrasive engagement with said pulpwood,whereby frequency of sharpening of said grinding member and themagnitude of grinding pressure variations to attain quality control arereduced.

A further object of the invention lies in the provision of a method ofgrinding pulpwood, which comprises advancing a plurality of pulpwoodsticks into abrasive engagement with a rotatable grind member.

Other objects and advantages of the invention will become more apparentduring the course of the following description, particularly when takenin connection with the accompanying drawings.

In the drawings, wherein like numerals designate like parts throughoutthe same:

FIGURE 1 is a top plan view of the apparatus effective to practice theinstant method, and incorporating a conical grinding member and apulpwood pocket which is moved laterally with respect thereto;

FIGURE 2 is a fragmentary end View to illustrate the grinding action ona pulpwood stick at the relatively larger radius of the conical pulpstone of FIGURE 1; and

FIGURE 3 is a view similar to FIGURE 2 and showing the grinding actionat the relatively smaller radius of the conical grinder stone.

As earlier stated, it has been difficult in the past to obtainconsistently uniform pulp quality at reasonable power expenditures, dueto the greater number of variables involved in the pulpwood grindingprocess. The freeness or measurement of pulp drainage characteristicschanges substantially from the time of stone sharpening until it againbecomes necessary to sharpen said stone, since it is now known that asharp stone tends to cut thefibers and decrease the fines, whereas asthe stone becomes Worn, the amount of cutting decreases and the rubbingand refining action tends to increase, producing more fines and greaterfibrillation. On the other hand, the variations in pulpwood moisturecontent and density require that the grinding pressure or unit loadingbe varied, and by reason of the relatively great contact area of theconventional grinder pocket, wide pressure variations or large changesin loading are necessary. This markedly increases the total powerrequirements for the grinding process, and a point is approached atwhich mechanical pulp grinding loses some of its economicalattractiveness.

It has now been discovered that uniformly consistent pulp quality atminimum power expenditures is obtained by varying the contact area ofthe pulp stone and pulpwood relative to one another, so that pulp stoneWear is reduced and the stone remains in relatively sharp condition fora longer period, and thereby continues to out rather than rub thefibers.

The relative movement described can be accomplished by moving thegrinder pocket laterally with respect to a generally conical grinderstone, or in other Ways which will become immediately apparent to thoseskilled in the art upon a consideration of the instant disclosure.

The apparatus is illustrated in FIGURE 1 and is clos ignated thereingenerally by the numeral ill. As shown,

there is provided a pulp stone or grinding member 71 of generallyfrusto-conical onfiguration supported for rotation at opposite ends byshaft means 72a journaled in bearing means 7373a, respecdvely, said pulpstone 71 being driven in rotation by motor means or the like '7 havingshaft means '75 coupled at 7'6 to shaft means 77 received in the bearingmeans 730.

To vary the grinding contact area, a grinder pocket or housing 73 isprovided with guide means 79 received in track means disposed generallyparallel to the grinding surface of the conical grinder 71. The pocket78 is laterally reciprocable along the track and suitable motive meansfor this purpose may take the form of a double acting cylinder havingports and 33 admit- \Lw ting pressurized fluid to opposite sides of apiston 8 having a rod portion connected either directly to the grinderpocket 78 or to the guide means '79 thereon. Pulpwood (not shown) in thepocket it? is urged into abrasive engagement with the conical grinder 71by means shown in FIGURE 1 as comprising a cylinder 35 provided withports 3% and S7 to reciprocate a piston ti? with arm portion connectedto plate means 8% bearing against the pulpwood sticlzs.

Buring lateral movement of the grinder pocket 78 along the track 89, thepulpwood sticks in the pocket 73 are continuously subjected to achanging stone radius, in the manner indicated in FEGURES 2 and 3. Thepulp stone 71 has a relatively large radius end 71:; and a relativelysmaller radius end 7122 between which the pulpwood sticks continuouslytravel under action of the motive means 81 for the grinder pocket 78. Byreason of the continuously changing grinding surface in abrasiveengagement with the pulwood, no single area or band along the pulp stoneis subjected to greater Wear, and the stone 71 accordingly longerretains a good tooth and the fibers from the pulpwood are cut, ratherthan rubbed, so that a minimum amount of fines are produced. it may beobserved upon reference to FEGURE 1 that a relatively small pocket 78 isutilized, presenting to the changing grinding radius a relativelysmaller contact area than has heretofore been employed with the resultthat not only is the sharpening eriod prolonged, but the powerrequirements to maintain the optimum unit loading or grinding pressureat the nip is markedly less than has previously been the practice.

It is apparent from the foregoing description that simultaneous movementof the grinder member and pulpwood sticlrs relative to one another canbe accomplished in numerous ways utilizing various structures. Theground pulp is of course collected in any convenient manner, andthereafter subjected to conventional processing steps. The apparatusdisclosed functions effectively on all known wood employed formechanical pulping, and customary pre-treatrnent may be utilized asdesired. in substitution for generally fiat grinding suriaces lyingparallel with the pocket and sticks being abraded, convoluted pulpstories may of course be employed and in this case the motion of thepocket can be relatively slower and the power requirements would ofcourse be reduced. This and other variations and modifications,including tie use of more than a single grinder pocket for each pulpstone, may of course be practiced without departing from the novelconcepts of the present invention.

1 claim as my invention:

1. Apparatus for grinding pulpwood to obtain pulp therefrom, comprisinga generally frusto-conical grinding member, means for rotating saidgrinding member, a housing for pulpwood positioned adjacent saidgrinding member, force applying means connected to said housing foradvancing said pulpwood into grinding contact with said grinding member,track means disposed generally parallel to the surface of said grindingmember and receiving said housing for movement .therealong, and motivemeans reciprocating said housing along the track means and laterallywith respect to said grinding member to vary the location of grindingcontact of said member with said pulpwood, whereby frequency ofsharpening of said grinding member and the power require ments to effectgrinding are reduced.

2. A pulpwood grinding mechanism comprising in combination a grindingrotor having a generally frusto-conical grinding surface, rotatingdriving means for driving the rotor in rotation about its axis, asupport for pulp wood adjacent said grinding surface for holdingpulpwood in grinding contact with a portion of the length of saidsurface, means operatively associated with said support for moving saidpulpwood support toward the surface to hold the pulpwood in grindingcontact, and linear drive means operatively associated with said supportrelatively moving the support in a general axial direction parallel tothe grinding surf-ace to progressively change the axial location ofgrinding contact between the pulpwood and grinding surface whereby thepulpwood progressively engages areas of the grinding surface of changingdiameter.

References Cited in the file of this patent UNITED STATES PATENTS 87,139Burghardt Feb. 23, 1869 491,971 Schmidt Apr. 23, 1889 492,425 Eilers, JrApr. 30, 1889 571,019. Roberts Nov. 10, 1896 1,476,032 Aicher Dec. 4,1923 FGREEGN PATENTS 20,141 Germany Nov. 22, 1882 41,073 Norway Mar. 9,1925 49,672 ermany Nov. 25, 1889 629,394 Germany May 6, 1936 682,946France Feb. 24, 1929

1. APPARATUS FOR GRINDING PULPWOOD TO OBTAIN PULP THEREFROM, COMPRISINGA GENERALLY FRUSTO-CONICAL GRINDING MEMBER, MEANS FOR ROTATING SAIDGRINDING MEMBER, A HOUSING FOR PULPWOOD POSITIONED ADJACENT SAIDGRINDING MEMBER, FORCE APPLYING MEAN CONNECTED TO SAID HOUSING FORADVANCING SAID PULPWOOD INTO GRINDING CONTACT WITH SAID GRINDING MEMBER,TRACK MEANS DISPOSED GENERALLY PARALLEL TO THE SURFACE OF SAID GRINDINGMEMBER AND RECEIVING SAID HOUSING FOR MOVEMENT THEREALONG, AND MOTIVEMEANS RECIPROCATING SAID HOUSING ALONG THE TRACK MEANS AND LATERALLYWITH RESPECT TO SAID GRINDING MEMBER TO VARY THE LOCATION OF GRINDINGCONTACT OF SAID MEMBER WITH SAID PULPWOOD, WHEREBY FREQUENCY OFSHARPENING OF SAID GRINDING MEMBER AND THE POWER REQUIREMENTS TO EFFECTGRINDING ARE REDUCED.